Relicensing is not easy and these days even releasing desktop krita on macos is a PITA thanks to Apple, even if we managed to get the code relicensed and port that to iOS we would need a dedicated team of devs for just satisfying the &%$# of Apple.

concerning s-pen actions, you indeed need to lift the stylus tip to use the gestures. The Samsung middleware works this way, I'm not aware of any option to change it. I usually tilt the stylus to the side for the button click gestures